text: In the lower deck, the solution is given by
  where  will satisfy a boundary-layer type equations driven by the pressure gradient  and the slip-velocity of order  generated by the middle deck. It is convenient to introduce  and , where  and  must satisfy
  These equations are subjected to the conditions
  where . The displacement function  and therefore  must be obtained as part of the solution. The above set of equations may resemble normal boundary-layer equations, however it has an elliptic character since the pressure gradient term now is non-local, i.e., the pressure gradient at a location  depends on other locations as well. Because of this, these equations are sometimes referred to as the interactive boundary-layer equations. The numerical solution of these equations were obtained by Jobe and Burggraf in 1974.